Panama's death followed five or so days of poor appetite and somewhat sluggish behavior. The aquarium staff responded with around-the-clock observation of Panama and regular blood work, which showed abnormalities, said aquarium chief executive officer David Yates.

The aquarium estimates Panama was close to 40 years old. The average lifespan of a dolphin in the wild is about 25 years, officials said.

The carcass will be sent to the University of Florida for a necropsy, Yates said.

"She's an older dolphin, so the likely cause of death was natural causes," Yates said. "We knew this would come at some point … but it's a sad day nonetheless."

Robin Bates, a trainer and supervisor of marine mammals at the aquarium, said she was already missing Panama's smooches and the way she loved to snuggle in her trainers' laps.

She and Yates said a dark mood and tears took hold of the aquarium Wednesday.

"She's a part of our family. We spend more time here than we do with our own families," Bates said, "so every animal here is a member of our extended family."

Officials say Panama — a bottlenose dolphin nicknamed "Granny" both because of her age and her strong-willed nature — was the first friend and tankmate of Winter, the dolphin with a prosthetic tail whose story inspired the Dolphin Tale movie.

Deaf when she was found stranded on a Panama City beach in 2000, Panama was rescued and brought to the Clearwater Marine Aquarium in 2001. She and Winter shared a tank until Winter's "sister," Hope, arrived in December 2010.

About three or four weeks ago, Yates said, all three female dolphins were moved to new outdoor tanks while their indoor tanks get repainted. The aquarium's male dolphin Nicholas is in a separate outdoor tank.

A recent Tampa Bay Times story documenting violations at the aquarium, including chipped paint inside the indoor dolphin tanks, quoted Walsh as saying that any move to a different tank is stressful for dolphins, especially for Panama because she's deaf.

However, Yates said Wednesday that the move outside and recent heavy rains played "zero" role in Panama's decline.

"If the move was an issue, you'd have seen this right away," he said, adding that over the years Panama had been successfully shuffled among "a number" of facilities without incident.

And water quality is tested daily in the outdoor tanks, he said.

"She actually was doing quite well for her age. You never would have suspected she was in her 40s," said Bates, the trainer.

The aquarium has experienced the deaths of two other dolphins in past years. Sunset Sam, blind in one eye and the aquarium's star performer before Winter, died of liver failure in 2001 at age 21. Dolphin Indie died in 2011.

Officials said Panama's death won't affect the filming of a sequel to Dolphin Tale that is scheduled to start production at the aquarium in October.

Keyonna Summers can be reached at (727) 445-4153 or ksummers@tampabay.com.